Fluorine-containing elastomers are molded into an O-ring, a hose, a stem seal, a shaft seal and a diaphragm and widely used in the fields of automobile industry, semiconductor industry and chemical industry because of their prominent heat resistance, chemical resistance, solvent resistance and fuel oil resistance. For fluorine-containing elastomers, a technique of undergoing a peroxide crosslinking reaction (for example, cf. JP53-125491A) and a technique of undergoing a polyol crosslinking reaction (for example, cf. JP53-4035B and JP6-128334A) have been generally employed.
However characteristics required therefor are becoming strict with progress of technology. In the fields of aeroplane and space, semiconductor manufacturing equipment, chemical plants and automobile industry, sealing property under higher temperature environment of more than 200° C. is demanded, and it is difficult to satisfy such requirements in the cases of molded articles and sealing materials obtained by conventional methods of peroxide crosslinking and polyol crosslinking.
To satisfy such requirements under higher temperature environment, proposals have been made to enhance heat resistance by improving a crosslinking system. For example, there are known a triazine crosslinking system forming a triazine ring with an organotin compound by using a fluorine-containing elastomer having cyano group introduced as a cure site (for example, cf. JP58-152041A), an oxazole crosslinking system forming an oxazole ring with bisaminophenol similarly by using a fluorine-containing elastomer having cyano group introduced as a cure site, an imidazole crosslinking system forming an imidazole ring with a bisdiaminophenyl compound (for example, cf. JP59-109546A) and a thiazole crosslinking system forming a thiazole ring with bisaminothiophenol (for example, cf. JP8-104789A), and a composition comprising a fluorine-containing elastomer having a carboxyl group as a cure site at an end of its trunk chain and/or its branched chain and an oxazole crosslinking agent, an imidazole crosslinking agent or a thiazole crosslinking agent (for example, cf. WO 00/29479).
However any of the proposals intended to use a perfluoro elastomer as a fluorine-containing elastomer, and there were no fluorine-containing elastomer compositions which are excellent in compression set at high temperature and are obtained by subjecting a nonperfluoro elastomer to the above-mentioned oxazole crosslinking, imidazole crosslinking or thiazole crosslinking.